This invention relates to imaging of radiation from within an animate or inanimate body using a probe that is insertable into the body.
In nuclear medicine, a commonly used technique for cancer detection involves injecting a radioisotope-labeled pharmaceutical which localizes preferentially in tumors. The location and extent of tumor can then be assessed by imaging the gamma ray emissions of the radioisotope using a gamma camera. Because of the limited spatial resolution and efficiency of existing gamma cameras as well as such considerations as patient dose and specificity of the tumor-seeking radiopharmaceutical, it has proved difficult in practice to image tumors smaller than one or two centimeters in size. Since early detection may be important for patient survival, it is important to detect the smallest possible tumors.
It is known that the sensitivity, resolution, and/or signal-to-noise ratio of detectors and gamma cameras can be increased using coded-aperture techniques. Uniformly redundant arrays and other coded apertures have been successfully employed to obtain images of radiation sources, with enhanced sensitivity, resolution, and/or signal-to-noise ratio. See, for example; R. G. Simpson and H. H. Barrett, "Coded-Aperture Imaging" (In "Imaging in Diagnostic Medicine"), p.p. 217-311. Plenum, New York, H. H. Barrett, "Fresnel Zone Plate Imaging in Nuclear Medicine", J. Nucl. Med. 13, 382 (1972); H. H. Barrett and F. A. Harrigan, "Fresnel Zone Plate Imaging of Gamma Rays; Theory". Applied Optics, 12 2686 (1973); U.S. Pat. Nos. 4,165,462, 4,209,780, and 4,262,207.
Small radiation detectors have been developed which can be inserted into the body in the immediate vicinity of the tumor, for example, during bronchoscopy or surgery. See, for example, H. B. Barber, et al., "Miniature Radiation Detectors for Surgical Tumor Staging", 32 ACEMB, Denver, Colo., 6-10 October 1979; H. B. Barber, et al., "Small Radiation Detectors for Bronchoscopic Tumor Localization", IEEE Transactions on Nuclear Science, Vol. NS-27, No. 1, February 1980. Such detectors have the advantage of increased count rate due to proximity to the source. A disadvantage of such detectors is that they are sensitive to radiation from all directions so that the unavoidable uptake of the radiopharmaceutical in normal tissue constitutes a significant background source. Any local nonuniformity of such uptake exacerbates the problem and makes the detection of small tumors more difficult.
It is an object of the invention to provide an improved system and method for obtaining information about radiation in a body.